Completing the apnea test: decline in complications

The apnea test is a crucial component of the clinical diagnosis of brain death. Apprehension about hypoxemia, hypotension, and/or cardiac arrhythmias may sometimes lead clinicians to avoid performing or prematurely terminate the apnea test. The purpose of this study was to perform a contemporary re-evaluation of the safety of the apnea test.

We performed a detailed chart review of consecutive brain dead patients who underwent an apnea test from 2008 to 2012.

Out of 63 patients, 33 were men (52.4 %). Mean age was 46.4 years. In all but four patients (93.7 %), the apnea test was performed by a neurointensivist. Infiltrates on chest radiographs were present in 34 (54 %). Seven patients (11.1 %) had chest tubes, six of which were associated with polytrauma. Echocardiograms were obtained in 47 patients (74.6 %), and 18 patients (38.3 %) had regional wall motion abnormalities (IQR 41-65 %). Fifty patients (79.4 %) were on vasopressors prior to apnea test. Median FiO2 was 0.5 (IQR 0.4-0.6), and PEEP was 5 cm H2O (IQR 5-10). After apnea test, median pO2 was 306 mmHg (IQR 121-389). Apnea test was aborted in only one patient; this patient had required FiO2 0.9-1.0 prior to the test and desaturated during the test. Mild hypoxemia occurred in three others without any consequences. Mild hypotension occurred in 11 patients (17.4 %) and was easily managed by an increase in the vasopressor infusion. There were no instances of major cardiac arrhythmias.

Apnea determined using the oxygenation diffusion method during brain death testing is very safe, provided appropriate prerequisites are met. We found a major decrease in the number of aborted or not attempted apnea tests compared to previous studies.